Re: [PATCH] Add support for ESRT loading under Xen

[Demi Marie Obenour <demi@xxxxxxxxxxxxxxxxxxxxxx>]

On Fri, Aug 26, 2022 at 09:53:29AM +0200, Jan Beulich wrote:
> On 25.08.2022 23:52, Demi Marie Obenour wrote:
> > @@ -40,6 +41,38 @@
> >  
> >  #define efi_data(op)       (op.u.efi_runtime_call)
> >  
> > +static_assert(XEN_PAGE_SHIFT == EFI_PAGE_SHIFT,
> > +              "Mismatch between EFI_PAGE_SHIFT and XEN_PAGE_SHIFT");
> > +
> > +bool xen_efi_mem_desc_lookup(u64 phys_addr, efi_memory_desc_t *md)
> > +{
> > +   struct xen_platform_op op = {
> > +           .cmd = XENPF_firmware_info,
> > +           .u.firmware_info = {
> > +                   .type = XEN_FW_EFI_INFO,
> > +                   .index = XEN_FW_EFI_MEM_INFO,
> > +                   .u.efi_info.mem.addr = phys_addr,
> > +                   .u.efi_info.mem.size = ((u64)-1ULL) - phys_addr,
> > +           }
> > +   };
> > +   union xenpf_efi_info *info = &op.u.firmware_info.u.efi_info;
> > +   int rc;
> > +
> > +   memset(md, 0, sizeof(*md)); /* initialize md even on failure */
> > +   rc = HYPERVISOR_platform_op(&op);
> > +   if (rc) {
> > +           pr_warn("Could not obtain information on address %llu from Xen: 
> > "
> > +                   "error %d\n", phys_addr, rc);
> > +           return false;
> > +   }
> > +
> > +   md->attribute = info->mem.attr;
> > +   md->type = info->mem.type;
> > +   md->num_pages = info->mem.size >> XEN_PAGE_SHIFT;
> > +   md->phys_addr = info->mem.addr;
> 
> As indicated in reply to your patch changing XEN_FW_EFI_MEM_INFO in
> the hypervisor: While this may fit the ESRT purpose, the address you
> return here is not necessarily the start of the region, and hence
> this function is not a general Xen replacement for the non-Xen
> function. Therefore I think it also shouldn't give the impression of
> doing so.

Is this just a matter of renaming the function?  Is it possible to
implement the original function with the current hypervisor?
-- 
Sincerely,
Demi Marie Obenour (she/her/hers)
Invisible Things Lab

Attachment: signature.asc
Description: PGP signature